The present invention relates to portable communication equipment which enables both transmission/reception of radiofrequency mobile telephony signals via a cellular network, and reception of radiofrequency television signals.
Mobile phones, which enable transmission and reception of radiofrequency telephony signals (namely voice but also messages, e-mails and multimedia content signals) via a cellular radiocommunication networks, are used now by a great percentage of the population. It is desirable to provide such mobile phones with additional functionalities. The reception of radiofrequency television signals are part of these new functionalities.
Today, two standards already exist in order to broadcast digital television signals on portable equipments, namely DVB-T, and DVB-H which is an adaptation of DVB-T for mobile equipments.
At the time being, only prototypes have been manufactured, which integrate, in the housing of a mobile handset, radiofrequency and signal processing modules enabling reception of television signals according to DVB-H standard. Once signals have been received and processed in order to extract digital television data, the visual part of television data is displayed on a display of the handset, while the sound part of television data is provided to a loudspeaker of the handset.
Main drawbacks of such integrated functionalities in a single handset are the following:
First, a dedicated antenna is needed for receiving radiofrequency television signals. However, in case of DVB-T, antenna of large size is required, which is incompatible with the generally desired compactness of the handset. For DVB-H standard, antenna can be of lower size. However, DVB-H standard will not be available in all countries at the same time, and should even be available much later than DVB-T standard in most cases. In addition, reception with DVB-H will probably be a paying service for the users, while DVB-T might be free.
A second important drawback is that transmission of radiofrequency telephony signals might interfere with reception of radiofrequency television signals. Since reception of television signals is concentrated on a small period of time (namely, 10% of the time is used for receiving television signals, while 90% of time is used for displaying received television signals), one cannot afford to take the risk to disturb the reception time with the transmission by the handset of a telephony signal.
One solution could be to forbid such transmission of the handset when the user is in a television display mode. However, this would lead to deprive the user of the basic functionality of his mobile phone, which is hardly conceivable. Additionally, most of the providers for television programs will be interested by the concept of interactive television. With this concept, the user of the television service would be asked to react in real time, for instance by sending a SMS or making a call. This means that a cellular return channel for transmitting telephony signals during periods of time in coincidence with television reception period would be compulsory. In this case, the transmission of telephony signals could interfere with the reception of television signals.